While a thin film with columnar microstructures is growing, a Motohiro-Taga interface is formed when the angle of inclination of the microstructures is abruptly altered in the vertical plane. Reflection of a normally incident plane wave by a Motohiro-Taga interface has been studied. If the plane wave is TE-polarized with respect to the plane contaming the directions of inclination of the columnar microstructures, it is not reflected by the interface; but a TM-polarized plane wave is partially reflected. Because of its polarization-discrimination property, the Motohiro-Taga interface will find application as the basis for devices in the upper millimeter wave and the lower infrared frequency ranges.